Electrical transformer



ELECTRICAL TRANSFORMER Filed June 29 1921 Snom/woz l2. Jij/gull@ 35% frio wol/14mg Wk Patented Dec. 8, 1925.

UNiTr-:D STATES PATENT o FFlcE.

HARRY NYQUIST, OF ELMHURST, NEW YORK, 'AlsS](1\l'.'91il T0 AMERICAN TELEPHONE AND TELEGRAPE COMPANY, A CORPORATION OF NEW YORK.

'ELECTRICAL TRANSFORMER.

application alec aan@ ae, leer. yseran nu. 481,319,

To all 'whom it may concern:

Be it known that l, HARRY NrQms'n'residving at Elmhurst, in the county of Queens and State of New York, have invented certain Improvements in Electrical Transformers, of which the following is a specification. Y

This invention relates to electrical transformers and es cially to a transformer arrangement use in signaling circuits for the purpose of connecting a two-wire circuit with a four-wire circuit.,

Heretofore it has been customary to connect a two-wire signaling circuit with a fourwire signaling-circuit by means of a transformer arrangement commonlykuown as a hybrid coil. The terminals of the windings of the hybrid coils are arranged in groups, one group being connected with the twowire circuit, another group being connected with the input side ofthe four-wire circuit, a third group being connected with the output side of the four-wire circuit and the ourth group being connected with a balanc-4 in network adapted to simulate the electrica characteristics of the two-wire circuit If the two-wire circuit is absolutely balanced by its networlr and likewise each two-wire branch of the four-wire circuit balances the other, the application of a difference of potential across the group of terminals connected with the output branch of the fourwire circuit, will cause current to iow in the two-wire circuit and also in the circuit of the balancing network, but there will be no resultant current in the two-wire branch'of the four-wire circuit which constitutes the input side of the four-wire circuit. Furthermore if a difference of potential is established across the two-wire circuit, current will be transmitted into each of the twowire branches ofthe four-wire circuit, but it will not be transmitted to the circuit containing the balancing network.

In connection with such transformer arran ements it has frequently been found dosira le to use filters 1n order to limit the range of 'frequencies transmitted from the range the apparatus for connecting the-twowire with the four-wire circuits that it vwill perform simultaneously the functionsof a filter and a transformer.

This inventionwill be better understood from the following description when read inr connection with' the attached drawing of which Figure l shows schematically an arrangement for carrying out the principle of this invention, and Fig. 2 shows the arrangement of the wmdings of the coils shown in l, which will serve to make clear the invention. Y

ln Fig, l, L; represents a high frequency two-wire transmission 'line which is to be connected" w1tl1 the four-wire circuit by means of the transformer arrangement indii cated b X," The form of arrangement represente in the figure comprises two transformers each of which has upon its core four windings which are wound in the same di- `rection, as shown 1n Fig. One terminal of each winding has been given an odd number and the other the'next higher even number. The windings have been wound in such a direction that when current flows from an odd to an even terminal the llux set up in the core is in a given direction irrespective of which winding is taken. The 'same would1 be trueiif current were to flow from an even numbered to an odd numbered terminal, but in this case the flux would of course be in the opposite direction.

As stated, the transformer arrangement X consists of two transformers, each comprising four windings. The windings of these coils are connected in groups of two each, which groups are associated with the various circuits connected to the transformer arrangement. Thus the group A is connected 'with the line L1, the group B with the input circuit of the four-wire circuit, group C with the circuit containing the balancing network N1 and group D with the output circuit .of the four-wire circuit. The winding 1 2 of oup A, together with the windings 3 4, $8 of group B and winding 5 6 of group C constitute one of the transformers of the transformer arrangement X, and in like manner winding 5 6 of group A, windings 3 4, 7 8 of group D and winding 1 2 of group C constitute the other transformer of.

. denser 23 in. group D. Since all of the groups are symmetrical, and the corresponding elements of each group have the same values, a balanced condition exists between the four circuits related to each other by the said transformer arrangement. lt will furthermore be apparent that the combination of the various groups constitutes in e'ect a high-pass lter which is adapted to transmit readily frequencies above a certain limit or to offer high im edance to the transmission of frequencies elow the said limit.

Having in mind the foregoing description of the circuit in which the invention is embodied, the invention will be understood from the following description of the mode of transmitting signals over the said circuit. Let it be assumed that energy is being transmitted over line L, from 'left to lto cause current to right, viz, in such direction as to impress its energyupon the four-wire circuit, and furthermore let the direction of flow of current at an instant in line L, be as indicated by the solid arrows. The current owing in wnding1 2 of group A willl induce a potential in the windings of group lB that will cause flow ofcurrent from 4 to 7 and will also induce a potential in winding 6 5 of group C that will .tend to cause a flow of current from 6 to 5. Similarly, the flow of lcurrent through windin 5 6 of group A, as indicated by the soli arrow, will induce a potential in the windings of group D that will cause dow of current from 4 to 7, and there will also be induced in winding 2 1 of group C a otential that will tend ow in the direction indicated by the solid arrow. llf the impedance ot the output circuit of' the fourwire circuit equals that of the inputcircuit, equal currents will exist in these circuits and as a result the potentials induced in the two windings of group C areequal in magnitude.D It will be seen, therefore, that no resultant electftakes place in the circuit of network N1. The current set up in group B will be transmitted in the direction of the arrows and will be amplified by the repeaters. will not be transmitted beyond the rst repeater in this two-wire branch of thc fourwire circuit since the repeaters associated therewith are adapted to transmit in only one direction, which direction is represented from right to left.

If, on the other hand, it is assumed that a signaling wave .is being transmitted from a distant station at the right over the twowire branch ,2 of the four-wire circuit and is being impressed upon group D of the transformer arrangement, the distribution of energy in the said arrangement is as follows: rlhe direction of flow of current of thev transmitted vwave in the group D `is represented, for example, by the dotted arrows, viz, the current'will flow through the windings of the said group in the direction from 7 Vto 4. rl`his flow of current will induce potentials in groups A and C, which are related to group D by'having oneo f their windings upon the same core. The potentials induced in windings 6 5 and 2 1 of groups A and C respectively will cause current to flow in the directions indicated by'tlie dotted arrows. Since the circuits of groups A and C are closed, current will owrin winding 2 1 and winding 5 6 of groups A and C respectively in the directions indicated 'by thev dotted arro'ws. If the impedance of N, equals that of Ll these currents will be of equal magnitude. In view of the fact that windings 2 1 and 5 6 of groups A and C respectively are upon the same magnetic core, and since the.

flow of current in winding 2 1 .of group The current setup in group D A is in opposite direction to theN flow of current in winding 5 6 of grou C (as may be clearly seen by considering t e distribution of windings shown in Fig. 2), no resultant iux occurs in the core, and consequently no induced potential results in the windings of group B. lConsequently the ener of 'the transmitted signaling wave,

whic is impressed upon group D by the rey peuters associated with the two-wire branch 2, is in turn impressed upon the two-wire line L1 and upon the circuit of network N but is not impressed upon group B associated with the other two-wire branch of the four-wire circuit. Consequently singing lio si ned to transmit frequencies above a certain limit, other frequencies will be practically excluded. It is therefore unnecessary to'insert in the line L1 and also in the circuit of the network N1 a filter to verform the function of excluding the un esired frequencies. The symmetrical groups, each containing two windings and acondenser, constitute, when combined, not only means for transferring energy from one circuit to another but also actas a filter to exclude undesired frequencies. The invention is not, however, limited to the articular arrangementshown since it will be apparent to those skilled'in the art that a different rearrangement of the elements constituting the groups will produce a combined transformer arrangement and a filter adaptedto transmit, for example, low frequencies arid to suppress high frequencies. -Orthe groups might be so designed as to transmit? only a cuit and,A arrangement of band of frequencies. The invention, therefore, is not limited to the particular elements constituting a group, or t a particular arrangement in the group, but lcovers broadly a transformer arrangement which, by'the arrangement of its windings and by the connection of condensers thereto, isadapted to function as a filter as well as a transformer. i

' Although this invention has been described as embodied in a certain form of cirarts, it is to be A understoodthat it is capab e of embodiment in 'other and different forms and arrangements without departin from the spirit and scope of the appended c aims. n

i 1. Ina signaling system, the combination with a line circuit of a balancing network circuit, an input circuit, an output circuit and a transformer arrangement adapted to Aelectrically connect all of said vcircuits and to transmit readilycurrents of frequencies above a certain limit.

, 2. In a signaling system,the combination,

with aline circuit of a balancing network, a. four-wire circuitcomprising an input cir'- cuit and an output c1rcuit,l and. a' transformer arrangement vcomprising 'a'.plurality of impedance groups, each containing a plurality of windings, and a condenser individual to each group adapted. to transmit currents of frequencies above a certain limit bet-Ween certain of said circuits.

3. In a transformer system the combination with a. plurality of transformers each having a plurality of windings,'one of the said windings of one transformer being connected with one winding of said other'transf former, and similarly another winding of the said irst'transformer being connected with another ,Winding of the said second transformer, thereby constituting four groups of windings, each group being conv two of the windin ductively separated'yfromithe othersffand allcircuit, an input circuit,- an output circuit, a plurality of transformers 'each having a' plurality of windings, certain of said windings being arranged in combination with a condenser lto form an impedance group, there'being one group for each of said 'circuits, and the oups being so related as to transmit readl y currents of g frequencies above a certain limit and to suppress those of other frequencies.

5. In a signaling system, thecombination with four circuits arranged in airs of approximately equal impedance, o a plurality of transformers each having theA 'same number of windings, the Ysaid windings being arranged in groups each containing a. lcondenser, each group being connected with--one of .said circuits, and the magnitude of the inductance of the windings and Ithe capacity of the condenser being so chosen that only those current of lfrequencies lying 'above-a lcertain limit owing through one group of windings will be transmitted-to thejwmdJ ings connected withv said other pair of circuits.,l Y 6. In an electrical transforming and filtering system, the combination vwith a plurality of transformers, each comprising a plurality ofwindings of a plurality of vcondensers, 'one condenser being connected seriall with of the first transfiirmer, the second con enser bein connected serially with two windings o the second transformer, lthe third being connected serially with the third windin of the first transformer and of the secon transformer,

loo

respectively, and the Yfourth condenser being seriall connected Vwith the fourth windings of t "e 'irs'tf-transformer-and of the' second transformer, respectively, the magnitude of the inducta-nce ofthe'windngs and :the capacit-y;l of the condensers being so chosen vas to limit therrange of frequencies t-ransformed'by the said system'.

7. In van `electrical epeatmg system,

combination with two transformers each comprismg .four wmdmgs arranged upon la magnetic core ofaI-line circuit connected with one winding ofi-each transformer a network circuit -connected with anot er winding `of each transformer, a repeater input circuit 4connected with-two windings of one transformerand a repeater output circuit connected "with twofwindings of the other transformer, each of the groups of windings connectedwith the said circuits having a. condenser in "series therewith, and

`the said groups'being so arranged as to transmit readily currents of frequencies ying above a certain limit sind to suppress all other frequencies.

8. in :i signallin system the combination withal, hybrid coi comprising four symmetric-ai impedance groups electro-magnetilcally relatedyeach group containing a, 'plurulity of inductance coils and a, condenser, of a plurality of circuits individual to end l@ connect-ed with the said impedance groups,

the constants of the said groups being so chosen as to transmm from one of seid circuits to certain of the other circuits e particular frequency or band of frequencies and June, 1921.

. f HARRY NYQUIST. 

